It can be empty, but you should always try to provide alternative text unless you have a seriously good reason not to do so. Be warned that by excluding a complete alt tag, visually impaired users will be unable to know that you have a picture in that placement.

Usually an emtyp alt attribute indicates that the image is purely decorative and ought to be added by the CSS rather than the HTML. Those in the HTML are usually there to convey some information and that information would need to go in the alt attribute for those who don't see the image.

Be warned that by excluding a complete alt tag, visually impaired users will be unable to know that you have a picture in that placement

They would know it's there if they have a screen reader. It'll say "graphic".

On a current site I've found myself using alt="" quite a lot. The reason being, background images can't be floated, where the text wraps around it, but the images are definitely decoration. Are there any good tricks for moving these things into the CSS?

My comment wasn't directed to you personally, Simon. Too many people use the same misnomer, even people who allegedly are professionals. It's as if a medical doctor would refer to the heart as a gland.

They would know it's there if they have a screen reader. It'll say "graphic".

On a current site I've found myself using alt="" quite a lot. The reason being, background images can't be floated, where the text wraps around it, but the images are definitely decoration. Are there any good tricks for moving these things into the CSS?

I use empty SPANs for that on the rare occasions I actually need to use them.

Yes, but the question was how screen readers handle an omitted (i.e., missing, not existing-but-empty) alt attribute.

Same as if it is empty. I thought someone believed it would say something when encountering an image if it had an empty alt attribute. But whether it is empty or non-existent altogether, it will be as though the image is not there.

I've heard a screen reader (may have been Window-Eyes, not sure) that would spell out the image URL (after saying the word 'image') in the absence of an alt attribute. That was a few years ago, though, so perhaps newer versions ignore it.

I've heard a screen reader (may have been Window-Eyes, not sure) that would spell out the image URL (after saying the word 'image') in the absence of an alt attribute. That was a few years ago, though, so perhaps newer versions ignore it.

In JAWS (which is what I use), it has an option to do that, but by default it reads the alt attribute and ignores it otherwise.

The only time it'll read the URL is if the image is within a link. But if someone neglected to put in an alt attribute, it is often the case that the image has a cryptic name as well, so it reveals no more information about the target of the link.

For instance, on this page, the five links after the logo have no alt attributes, so I hear something like this: